What is the percent slip for an 8-pole, 60 Hz motor with a nameplate speed of 875 RPM?

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Multiple Choice

What is the percent slip for an 8-pole, 60 Hz motor with a nameplate speed of 875 RPM?

Explanation:
Slip is how far the rotor speed falls behind the synchronous speed, expressed as a percentage of that synchronous speed. For an induction motor, Ns = 120 f / P. With f = 60 Hz and P = 8, the synchronous speed is 900 RPM. The rotor runs at 875 RPM under load, so slip s = (Ns − Nr)/Ns × 100% = (900 − 875)/900 × 100% = 25/900 × 100% ≈ 2.78%. So the percent slip is about 2.78%. For context, zero slip would mean the rotor is turning at 900 RPM; larger slips correspond to more lag (for example, 5.56% implies about 50 RPM slip, giving Nr ≈ 850 RPM).

Slip is how far the rotor speed falls behind the synchronous speed, expressed as a percentage of that synchronous speed. For an induction motor, Ns = 120 f / P. With f = 60 Hz and P = 8, the synchronous speed is 900 RPM. The rotor runs at 875 RPM under load, so slip s = (Ns − Nr)/Ns × 100% = (900 − 875)/900 × 100% = 25/900 × 100% ≈ 2.78%.

So the percent slip is about 2.78%. For context, zero slip would mean the rotor is turning at 900 RPM; larger slips correspond to more lag (for example, 5.56% implies about 50 RPM slip, giving Nr ≈ 850 RPM).

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